This invention relates generally to a rotary apparatus for use with a gasifier system, and, more specifically, to a rotary apparatus for use in transporting a solid particulate within a gasifier system.
Some known coal gasification systems use an entrained bed, non-catalytic, partial oxidation Texaco Gasification Process (TGP) in which carbonaceous feedstock reacts at elevated temperatures and pressures to produce synthetic gas that includes carbon monoxide and hydrogen. In at least some known gasification systems, carbonaceous feed, such as, high-rank bituminous coal, is first made into a slurry and is then pumped to a specially designed injector mounted at the top of the refractory-lined gasifier. As such, difficulties involved into feeding dry feedstock to the gasifier at high pressures are avoided. However, known slurry water may represent a thermal liability because the vaporization and heating of water increases oxygen consumption within the gasifier. Generally, however, at least some known gasification processes can tolerate the amount of water added to make bituminous coal slurries because bituminous coals naturally have higher energy contents and lower water contents than low-rank coals, such as sub-bituminous coals.
The natural moisture content of low-rank coals is generally comparable to the amount of water added to bituminous coal to make bituminous coal slurries. As such, slurry feeding low-rank coals to a gasifier may cause a thermal liability that is substantially greater than the thermal liability of bituminous coal slurries such that feeding low rank coals as slurries to the gasifier may be impractical. To overcome such problems, at least some known low-rank coals may be dried and then made into a slurry, such that the low-rank coal slurry fed to the gasifier has a reduced amount of water, as compared to low-rank coal slurries made with un-pre-dried low-rank coal. However, known moisture removal methods for low-rank coal may create additional difficulties if drying does not accompany changes in coal internal structures. As such, feeding dry low-lank coal is usually preferable to feeding a low-rank coal slurry or dried low-rank coal slurry.
Some known gasification systems that dry-feed coal into a gasifier use lock hoppers to supply feedstock to the gasifier. However, at least some known lock hoppers have difficulty supplying dry coal feedstock to entrained flow slagging gasifiers at pressures higher than approximately 30-40 bars (435-580 psi). However, some known entrained flow slagging gasifiers require a feedstock pressure higher than approximately 30-40 bars. To achieve higher pressures, at least some known lock hoppers use valves, fluidizing systems, and/or compressed fluidizing gases. However, in addition to the difficulties and complexities associated with such equipment, the gas consumption to fluidize ground coal in a pressurized lock hopper increases as the pressure increases. Furthermore, at least some known pressurized lock hoppers include a steep cone angle to facilitate the flow of ground coal. However, such a cone angle generally significantly increases the height of lock hopper. Other known gasification systems use a pump, rather than a lock hopper, to dry feed coal to the gasifier, however, the flow rates of such pumps are generally less than the coal feed rate corresponding to the gasifier capacity.
One known gasification system uses a pocketed wheel to transport liquid and coal particles to a fixed-bed, Lurgi-type gasifier at high pressures. However, such an apparatus is not configured to dry-feed feedstock to an entrained-flow type gasifier, which generally requires a higher feed pressure than a fixed-bed gasifier.
Some known entrained flow gasifiers discharge solids, or slag, from the bottom of the gasification process equipment. Such solids generally include the inorganic and metal components in the feedstock, for example, ash in coal, and a small amount of unconverted carbon. The solids are discharged from the bottom of known gasifiers intermittently through a lock hopper system. Generally, to remove slag through some known lock hopper systems, slag is first cooled directly or indirectly within the gasification process, and then enters the lock hopper through an automatic valve, and a lock hopper dump cycle is controlled by valve sequencing. However, such valve systems add complexity to the gasification system.